1. Field of the Invention
The present invention relates to a fuser-controlling apparatus. More particularly, the present invention relates to a fuser-controlling apparatus for generating a power synchronization signal regardless of the levels and frequencies of an applied power voltage, instantaneously carrying out power and phase controls, and controlling power to a fuser according to a detected level of the applied power voltage.
2. Description of the Related Art
The image-forming apparatus is a device for printing images on a recording medium such as paper, corresponding to original image data input. These devices include printers, photocopiers, facsimile machines, and so on.
Such an image-forming apparatus is necessarily provided with a device for keeping heat at a certain temperature in order to enable normal print jobs. In particular, a fuser is provided and has its surface continuously heat-maintained at an appropriate target temperature to fix toner images on paper.
FIG. 1 is a block diagram for illustrating a fuser-controlling apparatus of a conventional image-forming apparatus.
In FIG. 1, the conventional fuser-controlling apparatus 70 has a power input unit 20, a fuser-controlling circuit 30, and a main controller 40.
The switching mode power supply (SMPS) 10 of FIG. 1 is also provided and converts the AC power externally input to the power input unit 20 into a voltage of a certain level needed in the image-forming apparatus.
A temperature sensor (not shown) detects the temperature of a heater 60 installed in the fuser 50, and outputs the detected temperature to the main controller 40, so as to enable the main controller 40 to detect the temperature of the heater 60.
The main controller 40 controls the functions of the entire system, such as warming-up time, temperature upon warming-up, temperature upon printing, and so on. Further, the main controller 40 receives an output signal of the temperature sensor, and outputs a high or low signal to a transistor TR1 in order to increase or maintain a certain temperature at the heater 60, so as to control the temperature.
The base of transistor TR1 is connected to an output terminal of the main controller 40 so as to be switched according to the high or low signal output from the main controller 40.
The fuser-controlling circuit 30 has an optical coupler 35 therein, and the optical coupler 35 has a photo triac P-TRIAC1 and a triac TRIAC1. The photo triac P-TRIAC1 causes a light-emitting element 33B to emit light, operating with the switching of the transistor TR1. One end of the light-emitting element 33B is connected to the collector of the transistor TR1 in order for the transistor TR1 to switch a light-receiving element 33A on via the light-emitting element 33B.
Once the light-receiving element 33A is turned on, electric current is applied to the gate of the triac TRIAC1, so that the triac TRIAC1 is triggered and AC power is then applied to the fuser 50.
The photo triac P-TRIAC1 activates at the point where a power voltage crosses a zero point, thereby improving a power factor and reducing surge current. The triac TRIAC1 is therefore, also turned on at a point where the power voltage crosses a zero point and then the AC power is applied to the fuser 50.
In the conventional fuser-controlling circuit operating as above, the main controller does not have information regarding an input power voltage, but turns on the triac at a point wherein a power voltage crosses a zero point. Thus, if the main controller does not have information of a synchronization angle of power voltage, a problem occurs since it is difficult to improve the flicker characteristics due to irregular turn-on points.
Further, instantaneous power control is essential to satisfy regulations regarding the flickering due to the power consumption change rates. As noted above, since the instantaneous power control becomes impossible without information of an input power voltage phase, it is difficult to improve the flicker characteristics. In particular, problems exist when there is no phase information of an input power voltage. That is, turn-on angle control using the triac becomes impossible, as well as power-factor control, even upon controlling a chopping circuit using high-frequency switching elements.
Further, if the variation values of power consumption are not minimized through the instantaneous power control in the case of devices consuming significant thermal energy, such as high-speed and large-scale laser printers or photocopiers, it is difficult to satisfy regulations regarding flicker. It is therefore, a necessity to detect input power phases for such instantaneous power controls.
Further, for circuits typically used for detecting a synchronization angle of such a power voltage, the circuits detect a synchronization angle based on the level of a voltage or detect frequency information. However, a problem exists with such circuits since different circuits are applied depending on the existing power environments.
Accordingly, a need exists for a system and method for evaluating input power and providing substantially instantaneous power control of devices, such as a fuser.